1. Field of the Invention
The present invention is related to a power converter and particularly to a control circuit and method for the power converter controlling adaptive voltage position (AVP).
2. Brief Description of the Related Art
Due to the semiconductor technology being developed progressively, the digital products such as the computer and the peripherals thereof are capable of being upgraded continuously. The fast change of the manufacturing process for the semiconductor results in a variety of demands for the power source of the integrated circuit (IC) employed in the computer and the peripherals thereof. Hence, various combinations of voltage regulators using such as the boost converter and the buck converter to meet the need of different power sources of the integrated circuit become one of the most important factors to offer versatile digital products.
The light load efficiency of the power converter has been getting to be valued in the recent years; as to the power of the central processing unit (CPU), the technique of adaptive voltage position has been widely applied in the voltage regulator module (VRM). Several technical literatures related to designing the adaptive voltage position are listed in the following:    [1] Kaiwei Yao, Ming Xu, Yu Meng and Fred C. Lee, “Design Consideration for VRM Transient Response Based on the Output Impedence,” IEEE Trans. Power Electron., vol. 18, no. 6, pp. 1270-1277, November 2003.    [2] Martin Lee, Dan Chen, Kevin Huang, Chih Wen Liu, Ben Tai, “Modeling and Design for Novel Adaptive Voltage Position (AVP) Scheme for Multiphase VRMs,” IEEE Trans. Power Electron., vol. 23, no. 4, pp. 1733-1742, July 2008.    [3] Ching-Jan Chen, Dan Chen, Martin Lee, Eddie Kuo-Lung Tseng, “Design and Modeling of a Novel High-Gain Peak Current Control Scheme to achieve Adaptive Voltage Positioning for DC Power Converters,” PESC 2008.    [4] Jian Rong Huang, Sophia Chien-Hui Wang, Chia Jung Lee, Eddie Kuo-Lung Tseng, Dan Chen, “Native AVP Control Method for Constant Output Impedance of DC Power Converters,” in Proc. IEEE Power Electronics Specialists Conference., 2007, pp. 2023˜2028    [5] K. Yao, Y. Ren, J. Sun, K. Lee, M. Xu, J. Zhou, and F. C. Lee, “Adaptive voltage position design for voltage regulators,” in Proc. IEEE Applied Power Electronics Conf., 2004, Vol. 1, pp. 272-278.
Besides, in order to promote the efficiency, a concept of variable load line (VLL) shown in FIG. 1 has been proposed too. The variable load line means that a single phase converter is operated with the light load and multiphase converters are operated with the heavy load so as to promote the efficiency of the light load. Further, the maximum value and the minimum value of the output voltage of the converter keep the same regardless a phase or multiple phases are operated.
For instance, in FIG. 1, the load line 11 is a line representing one-phase converter operating with load current from 0 to 20 A; the load line 12 is a line representing two-phase converter operating with load current from 0 to 40 A; the load line 13 is a line representing three-phase converter operating with load current from 0 to 60 A; the load line 14 is a line representing four-phase converter operating with load current from 0 to 80 A. The maximum value Vmax and the minimum value Vmin of the output voltage of the converter for the load lines 11, 12, 13 and 14 are identical.
The control method for the power converter with adaptive voltage position disclosed in the preceding literatures are designed for the analog controller. Although it is capable of performing control of adaptive voltage position with negative load line with the output voltage decreasing during the load current increasing, it is incapable of performing control of adaptive voltage position with positive load line with the output voltage decreasing during the load current increasing. In addition, the load line of the power converter is unchangeable and it is incapable of offering the variable load line operated in the multiphase converter.